The work describes various physical and chemical treatments to eliminate the deleterious effects of impurities in phosphogypsum on the
delayed setting time and impaired strength development behaviour of cement to which it was added as a set regulator. The physical treatments
included washing, milling, and ultrasonic treatment of the material, while the chemical treatments dealt with acidic and basic additions to the
phosphogypsum during the washing stage. It was found that chemical treatment with a milk of lime solution, which is often recommended in
literature, was ineffective in reducing set retardation. Treatment with ammonium hydroxide or sulphuric acid was more effective in this
regard. Intergrinding phosphogypsum with slaked lime improved its effectiveness in reducing set retardation, but the use of unslaked lime
was less effective and also resulted in marked reductions in compressive strengths. A combined treatment of wet milling phosphogypsum
with a lime slurry in a ball mall was derived from these experiments and is recommended for full-scale plant applications.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:tut/oai:encore.tut.ac.za:d1000889 |
| Date | 21 January 2003 |
| Creators | Potgieter, JH, Potgieter, SS, McCrindle, RI, Strydom, CA |
| Publisher | Cement and Concrete Research |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | |
| Rights | c 2003 Elsevier Science Ltd. |
| Relation | Pergamon |
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